The present invention concerns amino ketone enantiomers and their direct preparation from an enantiomeric precursor using Friedel Crafts catalysis.
Aminoindanols of the formula: ##STR1## where R is H or CH.sub.3 are disclosed in the literature [(see e.g. E. Dornberger, Liebigs Ann. Chem. 743, 42-49 (1971); N. Levin et al., J. Org. Chem. 9, 380-391; R. V. Heinzelmann et al., J. Org. Chem. 14, 907-910; Remik et al., Lieb. Ann. Chem. 725, 116 (1969)]. The formula A compounds have two chiral centers at the 1 and 2 positions. Thus, four enantiomers, comprising two pairs, are possible. The enantiomeric pairs are designated as cis and trans. The Formula A compounds and their enantiomers are indicated to have pharmaceutical activity like ephedrine e.g. as bronchodilators.
Preparation of the A compounds is generally carried out by catalytic reduction of the corresponding ketone of the formula: ##STR2## which yields a mixture of enantiomers. A process has been discovered for direct preparation of a single enantiomer of Formula B which is then converted directly to a single enantiomer of Formula A.